The present invention relates to foam systems and rigid polyurethane foams prepared therefrom. More particularly, this invention relates to all-liquid foam systems and to high-density, rigid polyurethane foams prepared therefrom which have an ASTM E-84 Class 1 rating. The invention further relates to articles formed from the polyurethane foams.
Rigid polyurethane foams are well known and are commonly prepared from organic polyisocyanates and organic polyols together with known blowing agents, surfactants and catalysts for the reaction of —OH and —NCO groups. Such foams are used in construction, refrigeration and insulation applications because they may be prepared in a wide variety of densities and because they are substantially closed cellular structures which essentially fail to elastically deform. Rigid polyurethane foams are also commonly used in the decorative molding market. Such market includes such products as crown molding, chair rails, picture frames, ceiling medallions, louvers and the like. Historically, rigid, high-density polyurethane foams have not been used in large commercial applications because of their poor fire performance as set forth in the NFPA 101® Life Safety Code® Handbook. As a result, commercial decorative molding is limited to currently approved materials such as wood, plaster and concrete.
Fire performance requirements for rigid polyurethane foams have centered on achieving a Class 1 rating under the basic combustibility test set forth in American Society of Testing Materials (ASTM) E-84 “Standard Test Method for Surface Burning Characteristics of Building Materials” (approved Mar. 10, 2003), which is incorporated by reference herein in its entirety. The ASTM E-84 test is used to assess the spread of flame on the surface of a material. In this test, a 24 foot long by 18 inches wide foam specimen is exposed to a controlled air flow and flaming fire exposure, adjusted so as to spread a flame along the entire length of a select grade oak specimen in 5.5 minutes. Generally, the test is performed on core foam of chosen thickness but on occasion it is performed on faced products. Flame spread and smoke density are the two parameters measured in the test. The Flame Spread Index (FSI) takes into account both the rate and total distance of the propagation of a flame front, measured visually. The smoke factor is a time-integrated measurement of the occlusion of a visible beam of light. Material performance is put into categories, namely 0-25 flame spread index is class I, 26-75 is class II, and 76-225 is class III. A smoke limit of 450 or less is required in each of these classes. ASTM E-84 also has a number of other designations, such as Underwriters Laboratories 723, National Fire Prevention Association 255, or International Conference of Building Officials 8-1. For a detailed discussion of the ASTM E-84 test, reference is made, e.g., to U.S. Pat. No. 6,319,962, which is hereby incorporated by reference herein in its entirety.
As noted above, to receive an ASTM E-84 Class 1 rating, a foam must have a flame spread of 25 or less and a smoke developed density (or smoke generation) value of 450 or less. Using conventional urethane technology, high-density, typical rigid polyurethane foams have failed to meet ASTM E-84 Class 1 standards due to the large amount of fuel available for consumption at higher densities. Failures to meet Class 1 standards have historically been related to high smoke-developed densities.
Polyurethane foams described as rigid and flame retardant are disclosed, e.g., in U.S. Pat. Nos. 4,053,439; 4,407,981; 5,268,393 (also discloses flame-retardant flexible polyurethane foams); U.S. Pat. Nos. 5,874,021; and 6,130,267 (directed to both fire retardant rigid and fire retardant flexible polyurethane foams). Rigid polyurethane foams said to have an ASTM E-84 Class 1 rating are disclosed, e.g., in U.S. Pat. Nos. 4,797,428; 4,940,632; 5,102,919; and 6,319,962.
U.S. Pat. No. 4,053,439 to Chlystek reports a flame-retardant, low-smoke generating polyurethane foam having incorporated therein a flame-retardant and smoke-inhibiting composition comprising in combination a halogen-containing, fire-retardant organic material and at least one metallic salt of an organic polycarboxylic acid free of acid functionality. The Chlystek patent teaches that the halogen-containing compound may be a reactive or non-reactive halogen-containing compound or may be in the form of a halogenated compound containing active hydrogen groups such as a polyol. The composition may further contain a non-reactive phosphorus-containing flame retardant such as tris(chloroethyl)phosphate, tris(chloropropyl)-phosphate, tris(2,3-dichloropropyl)phosphate, tris(2,3-dibromopropyl)phosphate, bis(beta-chloroethyl)vinyl phosphate. Chlystek does not state whether the foam therein meets standards set forth in the ASTM E-84 test.
U.S. Pat. No. 4,407,981 to Aaronson reports a flame-retarded polyurethane foam containing polyurethane, a two-component flame retardant system consisting of an additive first flame retardant containing dialkyl alkylphosphonate and a second flame retardant containing organochlorine or organobromine (e.g., trichloroisopropyl alcohol or dibromoneopentyl glycol) incorporated in a polyether polyol. The Aaronson patent teaches that the polyurethane foam therein has a flame spread index of 0-75 and a smoke developed density of less than 450 when subjected to ASTM Test E-84. The flame spread index and smoke developed density of the Aaronson polyurethane foam appear to fall within the Class 2 standards of ASTM Test E-84.
U.S. Pat. No. 5,268,393 to Blount reports a rigid, flame retardant polyurethane foam consisting of the reaction product of an organic phosphorus-containing compound, a polyisocyanate, optionally a polyurethane catalyst, and optionally a foam stabilizer.
U.S. Pat. No. 5,874,021 to Inazawa et al. reports a method for making a low-fuming rigid polyurethane foam, involving foaming of a mixture containing a polymethylenepolyphenyl polyisocyanate or a modified material thereof, an aromatic polyester polyol, an aromatic polyether polyol, at least one metallic catalyst, a blowing agent which is an adduct of a primary or secondary amine compound with carbon dioxide, and, if necessary, a flame retardant and a surfactant. The only flame retardant specifically identified is tris(beta-chloropropyl)phosphate at col. 9, Table 2.
U.S. Pat. No. 6,130,267 to Dueber et al. reports flexible and rigid polyurethane foams formed from fire retardant compositions containing a dispersion of a solid fire retardant such as melamine, ammonium polyphosphate or guanidine carbonate in a liquid organic polyisocyanate which contains dispersed polymer particles.
As stated above, the aforementioned patents to Chlystek, Aaronson, Blount, Inazawa et al. and Dueber et al. do not disclose whether the rigid polyurethane foams taught therein meet ASTM E-84 Class 1 standards.
U.S. Pat. No. 4,797,428 to Reichmann reports rigid flame resistant polyurethane foams made by reacting an aromatic polyisocyanate with a mixture of 25-75% of an oligoester and another isocyanate-reactive material in the presence of a blowing agent at an NCO index of less than 300. The Reichmann patent teaches that the foams therein have an ASTM E-84 Class 1 rating and are particularly useful in construction applications. The patent teaches that the foams therein can have densities above and below 2 pcf. However, the highest foam density disclosed in the patent relative to the invention foam is 2.5 pcf (see col. 9, System F).
U.S. Pat. No. 4,940,632 to Nicola et al. reports an ASTM E-84 Class 1 rated polyurethane foam formed by reacting a polymethylene poly(phenyl)isocyanate-based isocyanate, one or more aromatic polyester polyols having hydroxyl functionalities of 2.4 or more and hydroxyl numbers of 350 or more, one or more polyether polyols having hydroxyl functionalities of 4 or more and hydroxyl numbers of 340 or more, one or more flame retardants, and one or more blowing agents, one or more catalysts, and one or more surfactants. Flame retardants which the patent to Nicola et al. teaches can be used therein include PHT4-diol and tris(chloropropyl)phosphate (Fyrol® PCF).
U.S. Pat. No. 5,102,919 to Swab reports rigid polyurethane/polyisocyanurate flame resistant foams, comprising an organic aromatic isocyanate, an active hydrogen-containing polyol component, a non-reactive flame retardant, a catalyst, co-blowing agents comprising water and a volatile blowing agent, a surfactant, optionally solubilizers, optionally fillers, pigments, crosslinkers or chain extenders, and an effective smoke-reducing amount of a mixture of dimethylesters of adipic acid, glutaric acid and succinic acid. Swab teaches that the foams therein have an ASTM E-84 Class 1 rating.
U.S. Pat. No. 6,319,962 to Singh et al. reports rigid polyurethane foams having improved flame resistance, wherein the foams are prepared from a composition containing an isocyanate, an isocyanate-reactive composition, a hydrocarbon/water blowing agent, and a phosphorus material. According to Singh et al., the foam therein meets ASTM E-84 Class 1 rating standards. The foam density is said to be less than 4.0 pcf, preferably less than 3.5 pcf, most preferably 2.0 pcf.
Although rigid polyurethane foams having an ASTM E-84 rating are reported in the art, high-density urethane molders continue to search for foam systems that can form high-density, rigid polyurethane foams meeting the ASTM E-84 Class 1 rating so as to be appropriate for use in, for example, large commercial decorative molding applications. It is further desirable that such foam systems have a processability similar to that of non-fire-rated foam systems so as to avoid having to use alternate or modified dispersing equipment.